Medical devices, such as implantable stents, have been coated with coating compositions comprising a therapeutic agent. One method of forming such coatings is to apply a coating composition containing a therapeutic agent to all the surfaces of the medical device. For example, for stents comprising a plurality of struts, all of the surfaces of the struts are coated with the coating composition to form a coating that encapsulates each of the struts. A reason for coating all the surfaces of the struts is to ensure that the coating remains on the struts by having the coating wrap around the struts.
In many medical devices, however, all of the surfaces of the medical device do not need to be coated with a coating composition comprising a therapeutic agent. For instance, in an intravascular stent, the inner or luminal surface of the strut may not have to be coated with a coating composition containing a therapeutic agent which is useful for treating the blood vessel wall, such as an anti-restenosis agent. This is because the luminal surfaces of the struts do not generally come in direct contact with the blood vessel wall to which the therapeutic agent is directed. Therefore, it is not necessary to coat the luminal surfaces of the struts with a coating composition containing such a therapeutic agent. The application of the coating to surfaces that do not need to be coated can result in undesired exposure of the patient to the therapeutic agent as well as increased costs of manufacturing the coated medical device associated with such increased use of the therapeutic agent.
Accordingly, there is a need for medical devices, such as stents, having coatings containing a therapeutic agent that sufficiently remain on the devices as well as coatings that reduce the undesired exposure of the patient to unnecessary amounts of therapeutic agents and that reduce the costs of manufacturing coated medical devices.